a) Field of the Invention
The present invention relates to a motor in which a magnet is fixed on the inner peripheral face of a circumferential wall part and a manufacturing method for the motor.
b) Description of the Related Art
In a motor in which a rotor is disposed on the inner side of a magnet that is fixed on the inner peripheral face of a circumferential wall part of a case, it has been proposed that a part of the case is cut and erected and the magnet is pressed and fixed with a fixing pin in order to fix the magnet on the inner peripheral face of the case, (see, for example, Japanese Utility Model Laid-Open No. Hei 03-60853).
Also, it has been proposed that a projection is formed in the circumferential wall part of a case and a magnet is sandwiched and fixed by the projection (see, for example, Japanese Utility Model Laid-Open No. Hei 02-53270).
Alternatively, it has been also proposed that, after a magnet is inserted into the circumferential wall part of a rotor, an adhesive is coated between the end face of the magnet on its opening part side and the circumferential wall part to adhesively fix the magnet on the circumferential wall part. It has been also proposed that a groove extended in an axial direction is formed on the circumferential wall part of a rotor and an adhesive is supplied from the groove (see, for example, Japanese Patent Laid-Open No. Hei 11-356026).
Further, it has been also proposed that a groove extended in an axial direction is formed on the outer peripheral face of a magnet and, after an adhesive is coated on the circumferential wall part of a yoke, the magnet is slid along the circumferential wall part of the yoke from the opening part side in the axial direction to be fixed (see, for example, Japanese Patent Laid-Open No. 2004-159384).
However, as described in the first prior art reference mentioned above, when a fixing member such as a fixing pin is used, the number of component parts increases and a lot of time and labor is required for the working operation and thus cost is increased. Further, as described in the second recited prior art reference, when a magnet is sandwiched and fixed by a projection or is press-fitted, debris of the magnet or a crack in the magnet may occur.
On the other hand, a method where a magnet is adhesively fixed as described in the third and fourth mentioned prior art references may eliminate the problems described in the first and second prior art references. However, as described in the third prior art reference, when adhesion is performed only between the end face of a magnet and the circumferential wall part of a case on the opening part side, or when an adhesive is supplied from a groove, the area of adhesion is small and thus a sufficient adhesive strength cannot be ensured. Further, as described in the fourth prior art reference, in the case that, after an adhesive is coated on the circumferential wall part of a yoke, a magnet is moved from the opening part side of the yoke in the axial direction along the circumferential wall part of the yoke, the adhesive may be in a sparse state on the opening part side of the yoke even when a groove is formed on the outer peripheral face of the magnet, and thus sufficient adhesive strength cannot be ensured.